The invention relates to a method for welding together two parts, wherein a concentrated beam of energy causing melting of the parts is directed into the gap extending continuously between the two parts.
Such a method is known in the state of the art and is used to weld together parts which are first slipped on to one another by, for example, a beam of electrons. This beam of electrons heats the material found on either side of the gap, which welds together by melting. This method has the disadvantage that not only is the material adjacent to the gap heated to a high temperature, but so is that found beyond the material in the length of the gap. In many cases damage may be caused by this, owing to which this method cannot be utilized. This despite the fact that such a method has important advantages, such as perfect fusion and requiring no special preliminary processing such as bevelling or accurate tolerance of the parts to be inserted into one another. Thus, it is not possible to weld together a shaft and a flange if, for structural reasons, a ball bearing or sealing ring, for example, must first be fitted on the shaft. One is therefore forced to use fastening techniques demanding accurate tolerances, such as shrinking-on, wherein, moreover, connections which are not very reliable are produced.
Two ways to avoid this disadvantage and make welding with a beam of energy possible are known in the state of the art.
First, the welding zone may be designed such that the remaining portion of the beam leaving the gap is absorbed at a suitably place by one of the parts to be welded together, so that damage to components found on the parts to be welded, such as sealing rings, bearings, etc., is avoided. However, this has the disadvantage that the base of the weld, which normally has faults such as porosity and cracks, comprises a structural part of the assembly. High stresses and defects present in this base may leak to crack formation in the stressed assembly and failure thereof.
A second way to prevent the beam of energy from being carried in further is the use of shields, which during welding are fitted between the exit and the part to be protected. Such shields, however, have only a limited service life and if space is limited, removal of these shields in construction of the fastening for the parts is especially difficult and costly.